The Houthis, a Shiite tribal militia from northwest Yemen, have been at war with the central government for the best part of a decade.

Recent Timeline:May 22, 1990 - The Republic of Yemen is created from the unification of North Yemen, the Yemen Arab Republic and South Yemen, the People's Democratic Republic of Yemen.

May 1994 - A civil war between northerners and southerners begins due to disagreements between supporters of Yemen's President Ali Abdullah Saleh, from North Yemen, and its Vice President Ali Salim al-Baid, from South Yemen. An estimated 5,000 people are killed. Troops loyal to President Saleh win the war in July.

October 12, 2000 -The USS Cole, at anchor in Aden, is bombed by al Qaeda, killing 17 US sailors.

October 2002 - Al Qaeda is blamed for an attack on the Limburg, a French-flagged oil tanker off the Yemeni coast.

September 23, 2006 - President Saleh wins re-election to a seven-year term with 77% of the vote.

September 17, 2008 - A terrorist attack on the US embassy in Sanaa leaves 16 dead, including six attackers.

December 28, 2009 - A Yemeni-based arm of al Qaeda, al Qaeda in the Arabian Peninsula (AQAP), claims responsibility for a failed bombing on a Northwest Airlines flight from Amsterdam to Detroit on December 25.

January 2, 2010 -US President Barack Obama announces a new counter-terrorism partnership with Yemen, involving intelligence sharing, military training and joint attacks.

January 3-5, 2010 - The United States and the United Kingdom temporarily close their embassies in Sanaa due to terror concerns.

February 11, 2011 - Protests begin in Yemen, inspired by the revolution in Egypt that ousted Hosni Mubarak. The demonstrations continue for months, while crackdowns on protesters lead to civilian deaths.

January 21, 2012 - Yemen's parliament approves a controversial law that ensures President Saleh complete immunity from prosecution.

February 21, 2012 - Yemen holds presidential elections to replace President Saleh. There is only one candidate on the ballot, Vice President Abdu Rabu Mansour Hadi, the acting president since November 2011. Hadi receives 99.8% of the 6.6 million votes cast.

February 25, 2012 - Abdu Rabu Mansour Hadi is sworn in as president of Yemen.

May 21, 2012 - A suicide bomber attack in Yemen kills over 100 Yemeni troops and wounds more than 200.

May 23, 2012 - Donor countries led by Saudi Arabia and the United Kingdom calling themselves the "Friends of Yemen" pledge more than $4 billion in aid.

December 5, 2013 -Militants stage a deadly attack on Yemen's Defense Ministry in Sanaa, ramming the building with an explosives-laden vehicle, followed by gunmen battling security forces inside. The attack targets a hospital at the Defense Ministry complex, according to the state-run Saba news agency. At least 52 people are killed in the attack, including four foreign doctors.

February 10, 2014 - President Hadi approves making Yemen a federal state consisting of six regions: two in the south, and four in the more populated north.

September 21, 2014 - President Hadi, Houthi rebels and representatives of major political parties sign an "immediate ceasefire, ending all forms of violence," according to a written statement. The UN-brokered deal ends a month of tense protests by Houthis that essentially halted life in Sanaa and resulted in hundreds of people being killed or injured.

January 17, 2015 - Houthi rebels kidnap President Hadi's Chief of Staff Ahmed bin Mubarak in a push for more political power. He is freed 10 days later.

January 20, 2015 - Houthi rebels take over the presidential palace.

January 22, 2015 - President Hadi resigns shortly after Prime Minister Khaled Bahah and the Cabinet step down. Houthis now control Sanaa.

February 11, 2015 - The United States and the United Kingdom suspend embassy operations in Yemen.

November 28, 2016 - The Iranian-backed Houthi movement forms a new government in the capital of Yemen. Abdul Aziz Habtoor, who defected from Hadi's government and joined the Houthi coalition in 2016, is its leader, according to the movement's news agency Saba.

February 8, 2017 - Nearly two weeks after an anti-terror raid authorized by US President Donald Trump kills civilians in Yemen, Yemen's government requests that the United States stop ground operations in the country unless it has the government's full approval.